In man-machine interaction scenarios, robots are usually expected to follow human gestures. In order to achieve this function, it is important to accurately measure the curving flexure (also known as curvature) of a person's finger. At present, many types of sensors are used to measure a curvature of a finger of a person. When a curvature of a finger of a person is large, these sensors can accurately measure the curvature of the finger. However, when the curvature of a finger of a person is small, these sensors usually fail to accurately measure the curvature of the finger. Thus, using existing sensors does not always accurately measure the curvature of a finger of a person.